Boulder dislodging tool



United States Patent Primary Examiner-Marvin A. Champion Assistant Examiner-Richard E. Favreau Attorney-wofford and Felsman ABSTRACT: Following is disclosed a tool for dislodging boulders from a hole being drilled in the earth. This tool includes a central shaft around which is secured a spiraled blade extending from the normally lower end of the shaft toward its upper end. In addition, the exterior edges of the blade diverge in a substantially conical manner from the lower end toward the upper endof the shaft. The pitch of the blade and the imaginary conical angle touched by its exterior edge are correlated to achieve an effective driving force which disrupts boulders from their supporting matrix such as shale. For superior results a pilot bit also having spiraled and tapered cutting edges is utilized on the lower end of the shaft.

Patented Nov. 3, 1970 1%.. Q aw 0 3 m Q? IN VENTOR.

ATTOR N E YS BOULDER DISLODGING TOOL BACKGROUND AND GENERAL DESCRIPTION When drilling shallow foundation holes, geological formations are sometimes encountered wherein boulders suspended in a matrix such as shale prevent effective penetration of conventional earth boring tools. The conventional auger for example cannot drill through boulders; cannot disintegrate them by wear or rupture; and cannot effectively dislodge them. Consequently, while the auger is a valuable and effective tool in drilling softer earth materials, it is often ineffectual in drilling formations containing boulders. It is my general purpose to provide an auger type tool useful with lightweight, shallow hole drilling equipment for effectively drilling through formations containing boulders.

It is difficult to fracture boulders with an auger type tool but ultimately l originated one which effectively dislodges boulders from shale matrixor equivalent. I found it necessary to generate unusually large driving forces to urge the tool through the formation and past the boulders. The required driving force is obtained through correlating the pitch of the auger flights on the tool and the conical angle which the exterior edges of the blade form, as seen in side elevation view. An additional cutting implement is provided on the end of said shaft, and in the preferred embodiment this cutting implement should have a configuration which is an extension of the configuration of the auger proper.

The above and other features of my invention will become apparent in the following detailed description and in the draw- BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF A PREFERRED EMBODIMENT The numeral 11 in the drawing designates a central shaft having secured to its upper end a connection means 13 which in this instance is in the form of a square tubular housing 14. Received by housing 14 is a kelly 15'which may be rotated and raised or lowered by a drilling rig or machine (not shown). A retainer pin 17 extends through apertures 19 and 21 in the housing 14 and through a mating aperture 23 in the kelly to secure connection means 13 and central shaft 11 to the kelly 15. The retainer pin 17 hasone enlarged end 24 and a transverse aperture 25 extending through the other end to receive a bolt (not shown) to secure the pin to the housing 14. There are otherconnection means used in the art for this purpose.

A spiral blade 27 extends from the normally lower end 29 of the central shaft 11 toward the normally upper end 31. The terms upper and lower" refer to the ends of the shaft as oriented in the vertical operating condition of FIG. 2. The exterior edge 33 of blade 27 tapers or diverges as seen in side elevation view from the lower end 29 to the upper end 31 of the central shaft 11. In the embodiment shown in the drawing the lower region 35 of exterior edge 33 of the blade 27 is essentially tangent to the central shaft 11 and extends progressively outward and upward until its upper region 37 spans a distance D transverse to central shaft 11. The edge 33 of blade 27 is preferably formed to intersect the central shaft 11 as shown in FIGS. 1 and 2.

Consequently the exterior edge 33 of the auger flight touches an imaginary line 39 which forms an angle alpha with a vertical line 41, as shown in FIG. 1. Angle alpha is selected typical instance is from 3% to 4 inches. The pitch P as indicated in FIG. 1' is selected from a range varying from about 9 to 12 inches, with best results being obtained at about eleven inches. 1

The lower end 29 of the central shaft has an extension or st inger 43 to which is secured by fastener 45 a pilot bit 47. The body of the pilot bit in this instance is substantially conical, having at least one spiraled or helical edge 49 which extends upward from the pointed lower region 51 to the truncated upper region 53 in the same manner as the spiraled blade 27. Hence, the pilot bit isin effect an extension of the spiraled blade. The pitch and helix angle of the cutting edge of the pilot bit may differ, however, from that of the spiraled blade 27. Since excessive forces are generated at the center and bottom of the bore hole, some variations are necessary from the design values established for the blade 27.

In operation the kelly 15 is lowered into the earth's forma-,

tion until the pilot bit 47 begins its penetration. Eventually the blade 27 engages the'earths formation and, due to the effective drive forces obtained through utilizing pitch P and angle alpha as previously described, large forces are transmitted from the blade to the boulders. As the blade moves under a boulder it exerts an upward and generally outward force that eventually rips the boulder from its supporting matrix. Neither the pilot bit nor the auger blade fracture or otherwise disintegrate boulders but rather dislodge them from the matrix. After a sufficient number of them have been dislodged, a conventional auger may be lowered into the bore hole to remove the boulders since my invention, due to its tapered construction, is not effective in lifting material.

If the pitch of the blade is too large, the tool will attempt to take too large a bite into the formation and may stall the drill from a range varying from 15 to 20, with best results being obtained at about 17 for a tool having a distance D of about 24 inches or larger. The diameter of the central shaft 11 in a rig power source when boulders are engaged, especially since a steep pitch decreases mechanical advantage. Conversely, if the pitch is too small the penetration rate decreases and the size boulders which may be dislodged decreases. As previously discussed, the size of angle alpha is correlated with the pitch to further insure an effective penetration rate while obtaining sufficient boulder disrupting force.

By utilizing apparatus as described above, bore holes may be effectively formed in earth formations containing large hard material such as boulders. By utilizing the pitch and angle alpha specified, optimum penetration rate and boulder disruption is obtained. While there are a number of forms of pilot bits available inv the art, the utilization of one having helical or spiraled cutting edges has been found most effective when used with my boulder disrupting tool.

While I have shown my invention in only one of its forms it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes and modifications without departing from the spirit thereof.

1 claim:

l. A boulder dislodging tool comprising:

a central shaft;

connection means on the normally upper end of said shaft for securing the tool to 'a rotating drill rig member;

a spiraled boulder dislodging blade extending from the normally lower end of said shaft toward said upper end;

said blade exterior edges divergingin a substantially conical manner from the lower toward the upper ends of said shaft, with the pitch of the blade being selected from a range varying from substantially 9 to 12 inches; and

a pilot bit secured to the lower end of said shaft.

2. The earth boring tool defined by claim 1 wherein said pilot bit has at least one spiraled cutting edge extending from a sharpened end region to an enlarged upper region that engages the lower end of said shaft.

3. The earth boring tool defined by claim 1 where the pitch of the blade is about 1 1 inches.

4. A boulder dislodging tool comprising: a central shaft; connection means on the normally upper end of said for securing the tool to a rotating drill rig member;

shaft a pilot bit secured to the lower end of said shaft.

5. The earth boring tool defined by claim 4 wherein said pilot bit has at least one spiraled blade extending from a sharpened end region to an enlarged upper region that engages the lower end of said shaft." v

6. The earth boring tool defined by claim 4 wherein said one half included angle is about l7 and said pitch is about ll inches. 

